Method for producing vinyl chloride-vinyl acetate copolymers in the form of their solid resins

Abstract

The invention provides a process for preparing vinyl chloride-vinyl acetate copolymers in the form of their solid resins by means of free-radically initiated suspension polymerization in aqueous medium of 70% to 90% by weight of vinyl chloride, 10% to 30% by weight of vinyl acetate and, if desired, further comonomers copolymerizable therewith, characterized in that 0.1% to 5% by weight of a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate is introduced as an initial charge, the amounts in % by weight being based in each case on the total weight of the comonomers.

1. A process for preparing vinyl chloride-vinyl acetate copolymers in the form of their solid resins by means of free-radically initiated suspension polymerization in aqueous medium, comprising polymerizing in a polymerization reactor 70% to 90% by weight of vinyl chloride, 10% to 30% by weight of vinyl acetate, optionally further comonomers copolymerizable therewith, the amounts in % by weight being based on the total weight of the comonomers being polymerized, wherein 0.1% to 5% based on the weight of the comonomers being polymerized of a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate is introduced into the polymerization reactor as an initial charge. 
     
     
       2. The process of  claim 1 , wherein 10% to 20% by weight of vinyl acetate and 80% to 90% by weight of vinyl chloride are copolymerized. 
     
     
       3. The process of  claim 1 , wherein additionally 0.1% to 10% by weight of ethylenically unsaturated monocarboxylic or dicarboxylic acids are copolymerized. 
     
     
       4. The process of  claim 1 , wherein additionally epoxide-containing monomers are copolymerized. 
     
     
       5. The process of  claim 1 , wherein during or after the polymerization, 0.001% to 0.1% by weight of ascorbic acid and/or isoascorbic acid, based on the total weight of the comonomers, is added, and optionally, in addition to the ascorbic acid and/or isoascorbic acid, citric acid is added in an amount of 0.001% to 0.1% by weight, based on the total weight of the comonomers. 
     
     
       6. The process of  claim 1 , wherein a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate comprising 15 to 85 weight percent vinyl acetate moieties is employed. 
     
     
       7. The process of  claim 2 , wherein additionally 0.1% to 10% by weight of ethylenically unsaturated monocarboxylic or dicarboxylic acids are copolymerized. 
     
     
       8. The process of  claim 2 , wherein additionally epoxide-containing monomers are copolymerized. 
     
     
       9. The process of  claim 3 , wherein additionally epoxide-containing monomers are copolymerized. 
     
     
       10. The process of  claim 2 , wherein during or after the polymerization, 0.001% to 0.1% by weight of ascorbic acid and/or isoascorbic acid, based on the total weight of the comonomers, is added, and optionally, in addition to the ascorbic acid and/or isoascorbic acid, citric acid is added in an amount of 0.001% to 0.1% by weight, based on the total weight of the comonomers. 
     
     
       11. The process of  claim 3 , wherein during or after the polymerization, 0.001% to 0.1% by weight of ascorbic acid and/or isoascorbic acid, based on the total weight of the comonomers, is added, and optionally, in addition to the ascorbic acid and/or isoascorbic acid, citric acid is added in an amount of 0.001% to 0.1% by weight, based on the total weight of the comonomers. 
     
     
       12. The process of  claim 4 , wherein during or after the polymerization, 0.001% to 0.1% by weight of ascorbic acid and/or isoascorbic acid, based on the total weight of the comonomers, is added, and optionally, in addition to the ascorbic acid and/or isoascorbic acid, citric acid is added in an amount of 0.001% to 0.1% by weight, based on the total weight of the comonomers. 
     
     
       13. The process of  claim 2 , wherein a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate comprising 15 to 85 weight percent vinyl acetate moieties is employed. 
     
     
       14. The process of  claim 3 , wherein a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate comprising 15 to 85 weight percent vinyl acetate moieties is employed. 
     
     
       15. The process of  claim 4 , wherein a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate comprising 15 to 85 weight percent vinyl acetate moieties is employed. 
     
     
       16. The process of  claim 5 , wherein a vinyl acetate-vinyl chloride copolymer soluble in ethyl acetate comprising 15 to 85 weight percent vinyl acetate moieties is employed. 
     
     
       17. A vinyl acetate and vinyl chloride copolymer in the form of a spherical particle powder, prepared by the process of  claim 1 , and the further process step of isolating polymer particles formed in the suspension polymerization and drying, the particles soluble in ethyl acetate at 20 weight percent solids to form a clear solution. 
     
     
       18. A vinyl acetate and vinyl chloride copolymer in the form of a spherical particle powder, prepared by the process of  claim 2 , and the further process step of isolating polymer particles formed in the suspension polymerization and drying, the particles soluble in ethyl acetate at 20 weight percent solids to form a clear solution. 
     
     
       19. A vinyl acetate and vinyl chloride copolymer in the form of a spherical particle powder, prepared by the process of  claim 3 , and the further process step of isolating polymer particles formed in the suspension polymerization and drying, the particles soluble in ethyl acetate at 20 weight percent solids to form a clear solution. 
     
     
       20. A vinyl acetate and vinyl chloride copolymer in the form of a spherical particle powder, prepared by the process of  claim 5 , and the further process step of isolating polymer particles formed in the suspension polymerization and drying, the particles soluble in ethyl acetate at 20 weight percent solids to form a clear solution.